1. Field of the Invention
The invention relates to thermoplastically moldable polyester resin compositions.
2. Brief Description of the Prior Art
Polyester resins having properties useful for thermoplastic molding, such as injection molding, are well known. However, not all of the known polyester resins are useful for injection molding. Especially difficult to injection mold are those polyester resins which possess hot-melt adhesive properties. Other polyester resins, although not considered to be hot-melt adhesives, are difficult to injection mold because they adhere strongly to metallic surfaces when in a heat-softened condition or following cooling and re-solidification. One class of such polyester resins are those obtained by the reaction of aromatic dicarboxylic acids with cyclo-aliphatic dialkanols. An example of such polyester resins is the one described in U.S. Pat. No. 2,901,466.
It will be appreciated by those skilled in the art of injection molding that these polyesters are generally unsuited for molding in conventional injection molding apparatus. The polyester wraps itself around the screw and adheres to the metallic surfaces of the injection molding machine.
However, these polyester resins have other physical properties which may be desirable in molded articles and in articles molded from blends of resins with compatible synthetic polymeric resins which are not themselves difficult to mold by thermoplastic molding techniques.
We have found that a particular class of mold release agents, added to these polyesters blended with polycarbonates provide thermoplastic compositions which are useful to injection mold a wide variety of articles. The agents do not significantly degrade the molded resin articles, in the proportions employed.